What did Galileo Galilei observe when turning his telescope toward the Milky Way in 1610?

An astonishing concentration of individual, unresolved points of light (stars).

In 1610, the Italian astronomer Galileo Galilei utilized his newly constructed telescope to examine the seemingly continuous luminous band identified as the Milky Way. Prior to this observation, it was understood only as a diffused glow or a smear of light. Galileo's revolutionary finding was that this apparent 'milk' was, in fact, composed of countless individual stars that were too distant or faint to be resolved by the naked eye. He specifically documented that the band was 'nothing else than a congeries of innumerable stars distributed in clusters,' marking the transition from mythological description to concrete astrophysical understanding of our galaxy's composition.